Method of saving metal values from slag.



No. 810,364. PATENTED JAN. 16, 1906.

v G. M; ALLEN. METHOD OF SAVING METAL VALUES FROM SLAG.

APPLICATION FILED SEPT. 1, 1904.

M/ITT HENTNEQEES v UNITED STATES PATENT OFFICE.

CHARLES M. ALLEN, OF LOLOQMONTANA.

, METHOD OF SAVING METAL VALUES FROM SLAG.

Specification of Letters Patent.

Patented Jan. 16, 1906.;

i gaaeon filed September 1,1204. Serial No. 222.934.

To all whom, it may concern:

Be i t known that 1, CHARLES M. ALLEN, of Lolo, in the county of Missoula and State of which the following is a full, clear, and exiict description, reference being had to the accompanying drawings, forming part of this vspeclflcation, in which the knife-blade edges at each side where the heaviest losses in matte-prills occur.

. The object of my invention is to provide means for more perfectly separating matteprills containing metal'values from worthless slags than in present pratioe; and to that end myinvention consists in conserving the original heat that exists in the slag and matte while in a smelting-furnace during their assage from the smelting-furnace into the f drehearth or separating-chamber'and also during the time of separation by gravity while in theforehearth or separating-chamber and' until the clean'worthless slag has been discharged therefrom;

. My inventionprovides an economical, convenient, and simple method of saving prills of matte that are lost unless a method such asI will now describe is used in connection with blast-furnaces provided with the large forehearths, such as have now been brought into general use for commercial reasons.

I Inpresent practice where matte-producing ores are smelted in blast-furnaces and Where the matte and slag flow out into a forehearth as fast as formed and are there separated by gravity the molten material is conveyed into the forehearth by a spout which is always left open onits top side, so that the molten material while traveling through this space, being exposed to the open air, will be materially cooled, and as a consequence will be rendered less fluid. The less fluid the slag becomes the more matte will be mechanically confined within it,and, per contra, the higher the heat the more liquid will-be the slag, and hence the more erfect will bethe separation of matte-prills y gravity. The chilling efect on matte and slag durin their travel through an open spout is evi enced by the constant formation of congealed accretions, which must be removed from the spout from time to time by hand as a means'of maintaining a continuousflow. Blocks of wood are constantly placed upon the spout in a feeble efiort to maintain the heat and to coun teract in part the chilling effect of the air. In

some instances brick arches have been constructed over the s out as a means ofaccomplishing the desire result; but the front end is always left open, and the result has not been satisfactory. Moreover, when the operator finds it necessary to work at the spout the entire brick structure above referredto must bedestroyed. The eneral ractice is to keep a stick. or block of wood ying over the running stream of molten material. This is expensive, as it consumes a large amount of wood, and neither the wood nor the brick arches rotect that portion of the stream that fa ls from the spout to the s ace below'the congealed slag-cover of the ore hearth. These expedients do notperfectly protect the stream while in the s out, .nor do they protect it at all during its all through the open air, where the greatest mischief is accomplished.

A furnace has been patented by J. B. F. Herreshoif in which the chilling of the slag or matte in their transit from a smelting-furnace into a separating-chamber is prevented by making the 'forehearth, in effect, a subdivision of the furnace itself. Herreshoffs device required the forehearth to be mounted on wheels; but when the large rectangular type ofblast-furnace came'into use and for commercial reasons largely superseded the smaller furnaces itwas foundnecessary at the same time to enlarge the forehearth to a diameter of from eight to twenty feet, so that it became impracticable to mount the foreat any time. The Herreshoff forehearth This entherefore can only be used with small round or oval blast-furnaces of the German type, which have been generally superseded.

In the Herreshoff portable forchearth the trappin of the blast by the r. Jlten bath is accomp ished by the water-ja :keted wall of the forehearth itself, and when the matte sep arates from the worthless slag it is thereupon removed from the forehearth by an ordmary ta hole. The slag alone passes from the over ow-spout after the separation. has been accomplished. The molten matte and slag therefore do not flow through a spout or trough or drop through the open air at all. It is imperative in the H'erreshoff apparatus that the forehearthshall be portable, because when anyobstruction occurs at the junctionpoint between the furnace and the foreearth it becomes .necessary that the forehearth should be removed in order that the operator may be able to rod the furnace and free the passage or orifice.

By my method an opening is provided in the front of .the spout-cover which may be closed or opened at will and which permits the furnaceman to rod the furnace at any time. Provision is also made so that the entire spout-covering may be raised Without *te diousdelayfiand without destroying the structure, and provision is made for the immediate replacement of the same when desired. The spout-cover is'preferably made of heavy metal, or it may be made of brick held together by a metal frame, or it may be molded in the form "of tiling. The connection from the spout to the top of the forehearth may also be made of metal, brick, or

tile, as above indicated, and any of these are so arranged that they will not be destroyed or disarranged by the removal of the spout- I .In the. drawings, 2 is-a water-jacketed c0pper-smelting furnace having a slag-spout 3, from which the molten slag overflows into a forehearth 4. 'The. spout is covered by a cover-'5, provided with a lifting device 6, by

which it may be raised to expose the top of the slag-sp'out. The cover has an end piece 5, whichwhen the cover isin place rests upon abridge 7'. and in conjunction therewith shields the stream of molten slag from the atmosphere from the point .whereit leaves the' furnace until it reaches the forehearth, and thus prevents the loss of heat and chilling of the s ag by radiation. The cover has pref- ;erably an. end opening. closed by a cap 8,

I which can be removed when it is desired to get access to the spout Without raising the cover.

9 is the overflow, from which the cleaned and worthless slag passes from the forehearth.

w the very best erases slag 11 which is allowed to form over forehearths .for the purpose of conserving the heat is apt to be thinner and unable to bear the weight of a man, because of the increased heat of the slag and matte, and bridges or supports are therefore needed for the workmen who have been accustomed to stand on such crust. Y The device which I have described above will tend to preserve the heat of the slag and matte and to make them more fluid and will thus produce a much better separation in the forehearth. It will also prevent the formation of the customary accretions of chilled slag that accumulate in the spouts of present furnaces and that now require removal by hand, because the radiation of heat from the cover is so great that it effectually prevents such accretions. r It is found in present practice that rod samples" taken of the slag do not show the full losses in matte-prills. Ladle samples of blast-furnace slag never show less than from .3 to .4 per cent of copper, and in many cases where poor work is done the slag carries as high as .7 per cent. of copper and a proportionate amount of precious metals. In the Butte district, Montana, in each pound of copper lost there is an additional loss of about four cents in precious metals. 'In other words, the precious-metal losses may approximate one-third of the value of the copper in addition to the loss of copper itself. About ten tons of slag is mad-e'for every ton of copper produced. Thus a loss of even .4 per .cent. in the slag would be equivalent to a loss of about 4.4 per cent. of the copper in the ore, to which, of course, must be added the value of the precious metals. Hixon in his work on copper-smelting states that the smelting loss at the Anaconda works under his management was 7.38 per cent. of the copper in the ore, and the converter loss' (which is also strictly a slag loss) was 2.238 per cent. of the copper in the ore. It will therefore be ap parent that my invention is of-great com-' mercial value,-for even a saving of .1 per cent. over present losses (even whenconsidering present practice) will amount to a saving 0 great slag losses that are now being made; My present invention will easily accomplish this result, and Ihave done much better in every-day work, inasmuch as I have made slags by this process carrying only a trace of copper and precious metals too small to deternnne byassay. In this connection it is wo thy of note that ordinary smelter practice is not at present conducted with averagelosses of only'.4 per cent. I havetested by assay slags from the dump-piles of several prominent Butte smelters that ran from .9 per cent. to 1.5 per cent. in copper and with the usual percentages of preclous metals.

at least one-quarter of the Moreover in present smelter practice it is customary to add fluxes to the ore charge, and Where oxidized iron is dificult to pro-- cure, as. is the casein the Butte district, the use of limestone flux is almost imperative, and the percentage of fluxes added to the ore charge is usually quite large; Theaddition of such fluxes adds proportionately to the tonnage of slag. Hence it adds proportionately to the prill losses of matte, and my present invention will make a proportionate saving in all such cases.

At many points ores of very loW grade are treated for their copper contents. At Ducktown, Tennessee; T1lt Cove, Newfoundland; Rio Tinto, Spain, and in the Greenwood district in British Columbia ores are smelted that run two per cent. and less in copper. The

smaller the copper, gold, and silver contents of the ore the greater-will be the relative proportion of worthless slag. Hence in present ractice the greater will be the proportion of oss relatively to the copper contents of the ore. It is not uncommon in present practice to thus lose one-third of the entire mineral values of the ores. In such cases my present. invention in reducing these slag losses to a mere trace can easily transform a smelting plant that is-a money-loser into a source of profit.

In the "best smelter plants of to-day the slag from the converters and refinery is poured 'into pigs, and on beingbroken u into pieces of suitable size is returned to t e blast-furnace, Where it acts as a flux and where its contained mineral values are partially recovered prior to its ultimate discharge tothe slagdump. My process is thereforefar-reaching -in its effects, inasmuch as it operates on the 4 made in copper-matte bla'st-smelters. Smeltlast and final treatment of all slags as now ing and converting losses up to this point are subject to future recovery; but beyond this point they enter the Waste-slag dump, and

therefore are beyond recovery.

' When matte and slag flow through a spout,

the matte, being the heavier of the two, necessarily flows on the bottom of the spout, and in this position it is covered on the top by the. slag, .and it is thus protected from the open air. The plastic lining of the trough itself soon becomes heated, and the matte stream is therefore at the same time protected against chilling on its under side. When the matte and the slag together are discharged from the front of the spout in their vertical fall into the forehearth, the matte may be seen on the rear side, or, in other Words, on

the under side of the stream, while the slag can be seen to envelop the front or top portion of the falling stream. Where'the slag .fiows in contact with the matte stream on each side, it thins out into knife-blade edges,

as indicated in Fig. 3, and as a consequence there is a portion of slag that thins out until it ceases altogether, while the rest of the stream 'consists of matte. edge at. the junction-line between the matte and the slagon each side of the falling stream is a rolific matte-gatherer, for, being exposed to t e open air,,it chills more rapidly than the central and thickerportion of the stream, and the viscidity thus produced causes it to entangle and to carry away mechanically steady streams of matte-prills on each side. In extreme cases portions of chilled slag that enter the forehearth often accumulateon the congealed slag-cover and build up the surface with matte and nlatte-prills through the partially-chilled and viscid condition of the slag. This is also the cause of much loss in mineral values. The flow from all copperblast furnaces is necessarily intermittent and irregular. It will vary With the rapidity of the smelting process. It also seems to pulsate and to throb, possibly through the generation of gases. When a salamander or a scaffold drops into the molten charge, a wave in the spout usually follows its drop into the bath. For the reasons stated the stream of molten material is greater at times than at others, and it constantly swells and subsides covering the forehearth and without uncov ering the spout. When the s out is thoroughly covered and protecte against the .outer air, as in, my present invention, all of these difficulties and expenses are avoided, inasmuch as the radiated heat from the cover maintains the molten stream without regard to its volume or its pulsations at practically the same temperature from the time it issues from the furnace until it is ultimately discharged at the opposite side of the forehearth as a thoroughly settled and cleaned slag for removalto the slag-dump.

The description above given will make, it clear that my apparatus as shown in the drawings is merely illustrative of my method and that it may be variously modified in order to suit the requirements of Varied conditions, since What I claim is- 1. 'The method of saving metal v alues from slags, which consists in withdrawing the slag and matte from beneath the surface of the molten bath, thereby tra pin the blast, and permitting them to over ow rom a furnacespout into a forehearth OPSGIJiLlLtiIlg-Clliillh bar, and conserving the original heat of the matte and slag by protecting them from the The very thin in its passage through the s out and through chilling effect of air during their flow into the forehearth or separating-chamber; substantially as described.

2. The method of saving metal values from sla s, which consists in withdrawing the slag an matte from beneath the surface of the molten bath, thereby trapping the blast, and permitting them to overflow from a furnacespout into a forehearth or separating-chamher, and conserving the original heat of the matte and slag by covering them throughout their entire transit into the forehearth substantially as described.

3. The method of saving'metalvalues from slags, which consists in withdrawing the slag 'and matte from beneath the surface of the molten bath, thereby trapping the blast, and permitting them to overflow from a furnace spout into a forehearth or separating-cham her, and conserving the original heat of the matte and slag by covering them' with heatradiating surfaces. throughout their entire transit into the forehearth; substantially as described.

4. The method of saving metal values from slags, which consists in withdrawing the slag and matte from beneath the surface of the molten bath, thereby tra pin the blast, and permitting them to overt ow l rom a furnacespout into a forehearth or separating-chamher, and conserving the original heat of the matte and slag by covering them with a pr 10- tically air-tight conduit which extends around the course of the fallin stream of slag, and into the slag-covering o' the forehearth substantially as described.

In testimony whereof I have hereunto set my hand.

CHARLES M. ALLEN.

Witnesses:

THOMAS H. BURKE, THOMAS C. MARsHALL. 

